Around 1400, the Golden Horde were stabilising as the Ottomans began to eye Europe. They had common threats (Timur, the PLC) and both were Sunni Muslim states. Could the two form a pact and, if so, what would be the possible ramifications? A surviving Horde? Islamic conquests? Political, cultural, economic effects?
Timur was dead in 1405 and not a factor anymore. The GH just defeated Lithuanian attempt to re-establish
Tokhtamysh (battle of Vorskla River, 1399) and, formally, united all Jochi's lands but it had internal problems: besides Khan it had a strong man, Edigu (head of the Nogai Horde) and if you look at the list of its Khans, you can easily find that during that period (all the way to 1435) their years in power had been rather short, which is indicator of the internal instability.
https://en.wikipedia.org/wiki/List_of_Khans_of_the_Golden_Horde
AFAIK, after Timur's raid the GH was in a deep economic depression because not only he destroyed the exiting cities on Volga but also broke many of the traditional trade routes.
The Ottomans also had to "recuperate" after being defeated by Timur.
Now, could their pact have some serious military consequences? I'm not too sure because they did not have the common enemies (Timur being dead). The Ottomans did not yet get in contact with Lithuania and the GH was too far away from the Balkans to be of any practical use to the Ottomans. Neither were the Ottomans in a good position (even if we are talking about the pure geography) to prevent the GH from falling apart or to defend the rump states from the future conquest by Moscow (Astrakhan is the only potential exception but the failed OTL expedition to Volga demonstrated numerous problems).
Economic effect is an interesting question to which I have no answer except that it
seems (to me) that these states had been operating along the different trade routes which had little in common. The main problem (for me) is that I have no idea what should happen to keep the GH intact.